“Most Unusual Expedition” Ever to Rely on Amateur Radio Ended 67 Years Ago

Sixty-seven years ago, on August 7, 1947, the maritime mobile station LI2B concluded its journey from South America by washing ashore on an island in French Polynesia. It was better known as the Kon-Tiki, a raft constructed largely from balsa logs. Norwegian explorer and ethnologist Thor Heyerdahl wanted to prove that people from South America may have migrated to Polynesia, and he took Amateur Radio along on his ocean journey.

A December 1947 QST article, “Kon-Tiki Communications — Well Done!” called the trip the “most unusual expedition ever to place reliance on Amateur Radio for communication.” The Kon-Tiki departed Peru for Polynesia on April 28, 1947. “It was the theory of Heyerdahl, [the] leader of the venture, that the settlement of the Pacific Islands resulted from a migration of American peoples who had sailed there many of years ago, rather than a trek from Asia as claimed by other scientists,” the QST article explained. Much later DNA evidence proved that Heyerdahl’s assumptions were at least partially correct.

The expedition carried three watertight radio transmitters — one for 40 and 20 meters, one for 10 meters, and a third on 6 meters. Each unit used 2E30 tubes, providing 10 W of RF input. (There was back-up radio gear aboard as well.) The Kon-Tiki also had onboard a National NC-173 receiver. Dry batteries, which proved problematic during the voyage, and a hand-cranked generator supplied the power. The QST article pointed out that proximity of the craft’s deck to salt water and the relatively small protection afforded by the thatched bamboo cabin meant that the radio gear would have to withstand the effects of moisture. As the article explained, C. F. Haddock, W1CTW, and H. A. Gardner, W1EHT, of the National Radio Company engineering staff took these considerations into account when designing and constructing the transmitting gear. The operators were Torstein Raaby and Knut Haugland, neither of whom with ham radio experience but both veteran radio operators.

For 3 weeks following the crew’s departure from Peru, the only radio contact Kon-Tiki had was with OBE, the station of the Peruvian Naval School. LI2B kept to a schedule, trying to contact key amateur stations on specified frequencies without success. Finally, on May 20, Harold Kempel, W6EVM, heard and worked LI2B on 14.142 MHz, providing the raft with its first North American contact. By mid-June, LI2B had worked numerous amateur stations, and as the trip progressed, a long-haul network of amateur stations developed. One of the network regulars was W3YA, the Penn State Amateur Radio Club station, which helped relay traffic to the Norwegian embassy in Washington. In the final month of the voyage, the 20 meter transmitter’s crystals all had failed, so the crew re-tuned the 10 meter transmitter to 13.990 MHz, the closest they could get to 20 meters.

One-half hour after being stranded, the QST article recounted, LI2B was fortunate to contact ZK1AB on Raratonga, who was asked to communicate with the Norwegian Embassy if LI2B was not heard within the next 36 hours. In his book Kon-Tiki, the basis for an Academy Award-winning documentary of the same name, Heyerdahl described the rush to make contact after landing on the reef, including the crew’s despair as the NC-173 slowly dried after getting soaked in the shipwreck, gradually receiving at higher and higher frequencies until eventually settling on a frequency high enough to make contact. The Amateur Radio transmitters still not operational, the operators employed a military transmitter powered by the hand-crank generator. Just before the specified period ended, LI2B contacted W0MNU, who relayed news of the landing, avoiding the need to send out rescue parties.